There are many systems available for mounting photovoltaic (PV) modules to building structures, such as a roof. These systems serve as a rigid interconnection element between a roof and a PV module to hold the modules in place and resist the forces of gravity and wind.
Traditionally, mounting systems consisted of a series of rail structures attached to the roof in columns and/or rows. Module clamps were used to attach the PV modules to these rail structures. Although effective at securing PV modules to the roof, these traditional systems required complex and time-consuming installations and utilized relatively large amount of materials. Eventually, pioneers in the solar industry, such as Jack West of San Rafael-based Zep Solar, realized that module frames themselves are sufficiently rigid to function as the rails of a PV mounting system. By utilizing the inherent rigidity of modules frames, system part counts and the corresponding costs of PV mounting systems were significantly reduced while installation time and overall aesthetics were improved. This realization caused the many in the residential solar industry to move away from rail-based solutions. However, in order to continue the momentum of solar against other fossil fuel-based energy sources, it is imperative that both hard and soft PV costs continue to be reduced.
Most contemporary rail-free or so-called direct mount systems, rely on pillar-like PV module supports which connect to each module frame at various points around the array—typically at least four points on each module. These module supports are in turn attached to the roof, either into a roof rafter or directly to the roof deck, via a flashing. The flashing is simply a flat sheet of rust-resistant metal, such as aluminum, often with one or more preformed features that are designed to mate with the module support. Flashings also typically include at least one lag-bolt through-hole for securing both the flashing and the module support to the roof.
While flashings are effective at preventing water leaks caused by the lag bolt, and also at covering errant drill holes that miss the roof rafter, they can increase the time of installation because when they are used, the installer must complete all site preparation first before placing any of the PV modules, installing a flashing at each intended roof penetration. This bottleneck prevents an installer from installing the array row-by-row or panel-by-panel and, as a result, may slow-down the rate at which PV can be installed, may require larger installation crews, or both. Also, because each flashing gets tucked underneath the next up-roof course of shingles, it is often necessary to remove existing roofing nails to accommodate the flashings. The installer must then be careful to apply sealant to each of these holes to prevent leaks. Therefore, each time an existing roofing nail is removed, a new potential leak point is created. Finally, each flashing adds a material cost to each solar installation that becomes significant when multiplied against every roof penetration of every installed array. This is especially true if the flashing has custom features or rubber parts requiring custom manufacturing.
Another problem with flashing-based mounting systems as well as flashing-less direct mount systems is that the area around an intended point of attachment of a PV mounting bracket may not be flat. This could be caused by the presence of a seam of overlapping shingles at the desired placement point, warping of the roof deck, and/or lack of uniformity in the roof joists or other roof components. As a result, although a lag bolt should generally be drilled normal to the surface of a rafter to provide the greatest pull-out resistance, normal to the roof rafter may not be normal to the portion of the roof surface contacted by the PV mounting bracket.
Accordingly, there is a need for a rail-free PV mounting system that enjoys the benefits of existing rail-free solutions, while reducing costs, and increasing installation times relative to such systems. There is also a need for a rail-free PV mounting system that is capable of compensating for planar variations in a roof surface.